Two evaporator refrigerating system



Jan. 15, 1957 R. w. DOEG 2,777,297

TWO EVAPORATOR REFRIGERATING SYSTEM Filed July 21,-1953 2 Sheets-Sheet 2 INVENTOR. E4525 h! D056 United States Patent TWO EVAPORATOR REFRIGERATING SYSTEM Ralph W. Doeg, Detroit, Mich., assignor to Nash-Kelvinator Corporation, Detroit, Mich., a corporation of Maryland Application July '21, I953, Serial No. 369,307

1 Claim. (Cl. 62--'-3) This invention relates generally to refrigerating apparatus and more particularly to two-temperature single circuit refrigerating systems.

It is an object of the present invention to provide an improved two-temperature refrigerating system in which flow of refrigerant from a relatively high temperature evaporator to a relatively low temperature evaporator in series circuit therewith is controlled to maintain a substantially constant pressure difference between the two evaporators while at the same time permitting the compressor to unload during the off phase of the refrigerating cycle by equalizing pressures throughout the system at that time.

Another object of the invention is to provide a pressure responsive valve controlling flow of refrigerant from one to another of series connected evaporators to maintain a substantially constant pressure difference between said evaporators, and to provide for by-passing some refrigerant from the first evaporator to the second to provide for unloading the compressor of the refrigerating system.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a vertical sectional view of a household type refrigerator embodying features of my invention; and

Fig. 2 is a substantially diagrammatical view of my improved two temperature refrigerating system.

Referring to the drawings by characters of reference, the refrigerating apparatus shown in Fig. 1 has a cabinet, designated generally by the numeral 20. The cabinet 20 comprises in general, a sheet metal casing 22 and a'sheet metal liner 24. Heat insulating material 26 of any of the well known suitable types may be interposed between the walls of the casing 22 and liner 24 to decrease the rate of leakage of heat into the interior of the cabinet. The liner 24 forms a food storage compartment 28 which has an access opening at the front of the cabinet, closed by a hinged door 30. In the lower region of the cabinet 20, below the food storage compartment 28, a machinery compartment 32 may be provided and may be closed at the front of the cabinet by a suitable door 34. This door 34 may be hinged along its bottom edge to the cabinet and may carry a storage bin 36 on the inner side thereof, if desired.

The refrigerating system comprises in general, a relatively low temperature refrigerant evaporator 38, a relatively high temperature refrigerant evaporator 40 and a refrigerant condensing element 42. The condensing element 42 comprises a refrigerant condenser 44 and a sealed refrigerant motor-compressor unit 46. The freezing evaporator 38 is preferably located in the upper region of the food storage compartment 28 and may be suspended from the top wall of the liner 24 by suitable brackets 50. Preferably, the relatively high temperature evaporator 40 is arranged in good heat transfer relationship with the liner 24 in a manner to cool the lower region of the food 2,777,297 Patented Jan. 15, 1957 storage compartment 28. For example, the evaporator 40 may be bent in sinuous form and be arranged to extend along the bottom wall of the liner 24 and partway up the rear wall thereof in contact with the outer surface thereof. Any suitable cement or other attaching means may be used to attach the evaporator coil 40 securely to the liner in good heat transfer relationship therewith. As shown in Fig. 1, the condensing unit 42, comprising the condenser 44 and motor-compressor unit 46 may be located in the machinery compartment 32. The numeral 52 designates generally a flue which is located at the back of the machinery compartment 32 to induce flow of air upwardly through the machinery compartment for cooling the same.

A number of shelves 54 are provided in the food storage compartment 28 and may be slidably supported on spaced pins 55 which may be secured to the liner side walls of the cabinet. A lower region of the food storage compartment may be closed at the front of the cabinet by inner doors 56. These doors 56 prevent rush of room air into the cabinet when the outer door 30 is opened and cooperate with the lower shelves 54 to decrease air circulation in the cabinet so as to effect a relatively lower humidity in the lower region of the compartment, suitable for the preservation of fresh vegetables.

The evaporator 38 may be of any suitable type capable of cooling the upper region of the food storage compartment and preferably also capable of freezing ice cubes. In construction, the evaporator 38 may be made of sheet metal, formed in the Well known U-shape to provide a box-like structure for receiving ice trays (not shown). Preferably, the front of the U-shaped evaporator 38 is closed by a door 58. Immediately beneath the evaporator 38, a drip pan 60 may be suspended by depending supports 56 which may be secured to the sides of the evaporator. If desired, a food container 62 may be supported immediately beneath the drip pan 60 on the uppermost of the shelves 54. The container 62 is located in close proximity to the freezing evaporator 38 to contain food or other things which require refrigeration to a lower temperature than the average temperature of the food storage compartment.

Liquid refrigerant is supplied from the condenser 44 to the relatively high temperature evaporator 40 through a small diameter or capillary tube 64 and gaseous refrigerant is returned from the freezing evaporator 38 through a return conduit 66 to the motor-compressor unit 46. A conduit 68 connects the relatively high temperature evaporator 40 to the inlet of the relatively low temperature or freezing evaporator 38 and interposed in this conduit is a pressure differential valve, designated generally by the numeral 70. The valve 70 acts to maintain a desired, substantially constant pressure difference between the two evaporators 40 and 38. Any suitable pressure responsive valve may be used for this purpose and may be arranged to maintain the pressure and temperature of the evaporator 40 above the temperature at which freezing would occur in the lower region of the food storage compartment. The valve shown in the present system includes a valve casing 72 having an inlet 74 and an outlet 76 which are respectively connected to the evaporators 40 and 38. In the casing 72, there is a port and valve seat 78 which is controlled by a pressure responsive valve proper 80. The valve proper 80 has a weight 82 which determines the pressure difference between the evaporators. This weight 82 and pressure in evaporator 38 act to seat the valve 80 and the force of the refrigerant leaving evaporator 40 tends to open the valve.

In accordance with my invention I provide a by-pass around the valve member 80 connecting the evaporators 40 and 38. The by-pass 100 may be in the form of a small diameter or capillary tube, as illustrated in Fig. 2,

having one endconnected to the conduit 68 and the other end connected to the evaporator 38 adjacent the inlet thereof. Although I have illustrated the by-pass diagrammatlcally and in the form of a capillary tube, it will be understood that this by-pass 100 may be located in the valve casing 62 by drilling or otherwise providing a small passage from the inlet 64 to the outlet 66 around the valve member 80 or if desired the valve seat may be scored to provide the desired by-pass, which in the present instance offers more resistance to the flow of refrigerant to evaporator 38 than that offered by valve 70.

In the operation of the herein described refrigerating system, liquid refrigerant is supplied by the capillary tube 64 to the evaporator 40 where some of the liquid refrigerant evaporates to cool the lower region of the food storage compartment by absorbing heat from the liner 24. From the evaporator 40, liquid refrigerant passes through conduit 68 to the control valve 70 and then to the freezing evaporator 38. A control or thermostat (not shown) may be provided to control the operation of the system. Such a control, as is well known in the refrigeration art controls operation of the motor-compressor, determining the cycle of operation thereof in response to the temperature of either evaporator as desired and that such controls are adjustable to obtain so-called cold control and fast freezing. When the system is shut down, the by-pass serves the purpose of permitting equalization of the pressures of the high and low sides of the system so that the pressure is equalized throughout the system. At this time the refrigerant on the high pressure portion of the system passes out of the condenser and through the evaporator 40, by-pass 100, evaporator 38 to the inlet side of the compressor to thereby equalize the pressure throughout the system. This unloads the compressor in the well known manner by permitting it to resume operation at a high pressure instead of the low pressure which would exist in the freezing evaporator if it were not for the by-pass 100.

Although only a preferred form of the invention has been illustrated, and that form described in detail, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claim.

I claim:

In a refrigerating system, a refrigerant condensing element, a relatively low temperature refrigerant evaporator having an inlet connected to said condensing element and having an outlet, a relatively high temperature refrigerant evaporator having an outlet connected to the inlet of said relatively low-temperature evaporator and having an inlet connected to said condensing element, a pressure differential valve interposed in the refrigerant circuit between the outlet of said relatively high temperature evaporator and the inlet of said relatively low temperature evaporator acting to maintain a predetermined pressure differential between said evaporators, and :1 small diameter tube by-pass having a flow capacity less than the ,flow capacity of said valve connecting the outlet of said 'relatively high temperature evaporator to the inlet of said relatively low temperature evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 1,768,602 Hull July 1, 1930 2,455,850 Atchison Dec. 7, 1948 2,515,825 Grant July 18, 1950 2,565,145 Mufily Aug. 21, 1951 

